Many antimicrobial agents are applied as solutions in water or another solvent. Application of such antimicrobial solutions results in wetting of the object treated. Certain antimicrobial agents are gases under ambient conditions. Such antimicrobial agents will typically not wet an object, they are difficult to retain on an object, and they can readily spread and pose toxicity problems.
Supercritical fluids have characteristics of both gases and liquids, but they have never been successfully used for applying antimicrobial agents. Characteristics of supercritical fluids have been documented in several editions of the CRC Handbook of Chemistry and Physics (e.g. pages F-62 to F-64 of the 67th edition, 1986-1987; or pages F66-F67 of the 64th edition, 1983-1984, both published by the CRC Press, Inc., Boca Raton, Fla.).
Supercritical fluids have been used as a medium for synthesis for chromatography of compounds. For example, supercritical carbon dioxide has been used as a reaction medium for alkylation reactions, polymerization reactions, and for complete oxidation of undesired contaminants to carbon dioxide, carbon monoxide and water. Another common application for supercritical fluids is in the extraction of desired compounds from liquid and solid substrates. For example, commercial supercritical extraction chromatography (SFC) uses the extraction capability of the supercritical fluid to isolate compounds, from various substrates, for analytical analysis. Commercially many applications for extraction of colorants, flavorings, and fragrances are known and, on a large industrial scale, caffeine is extracted from coffee and tea. Supercritical fluids have not been employed for effective generation of active antimicrobial agents.
Accordingly, a substantial need exists for improved methods for generating and/or applying antimicrobial agents employing near critical, critical, or supercritical fluids.